Typical vehicles whether automobiles, fire trucks, garbage trucks, cement mixers, multiwheel drive trucks, military transport trucks, etc. include a combustion engine mechanically coupled to the driven wheels. This coupling typically takes the form of a clutch or torque converter coupled to a multispeed transmission which is coupled to the driven wheels. More specifically, the driven wheels are usually driven in pairs through a differential coupled to the transmission by an appropriate drive train e.g. drive shaft, angle drive, etc.
While this type of drive train is highly reliable, efficient based upon mature technology, it is relatively expensive in comparison to the other components of the vehicle. Additionally, cost effective transmissions typically require engine oversizing to provide suitable vehicle speed surges. Thus, to save transmission cost, there is an increase in engine cost and vise versa. The ultimate selection is ultimately determined by performance and cost requirements.
In attempts to reduce the complexity and cost of drive trains electric and hydrostatic drives have been considered. However, these types of drives have proven to be too inefficient to be practical. Accordingly, it would be desirable to provide a hybrid drive which combines the cost savings and flexibility of an electric motor drive with the efficiency of a combustion engine based drive.